Field of the Invention
This invention relates in general to the field of cellular communications, and more particularly to a mechanism for performing circuit switched fallback in a single radio dual mode cellular system.
Description of the Related Art
The cell phone industry is undergoing exponential growth, not only in this country, but all over the world. In fact, it is well known that the over twenty percent of the adult population in the United States do not even have a traditional landline telephone. In addition to those who do not own a conventional telephone, nearly ninety percent of the adult population owns a wireless phone.
And the usage of cell phones is increasing as well over the use of traditional landline telephone coverage. In fact, one in seven adults now uses only cell phones. Whereas in the past cell phones were used when a landline was not available or under emergency conditions, lower carrier rates, affordability of family packages, and free mobile-to-mobile or friend-to-friend promotions have fostered in significant increases in usage. It is not uncommon today to walk into any public forum or facility and notice a majority of the people there talking on their cell phones.
The ability to communicate using a mobile phone, or mobile station, has been available since the middle of the last century. However, during the 1990's so-called “2G” or second generation mobile phone systems were provided that began the growth in both deployment and usage that we currently enjoy today. These initial systems predominately provided for the routing and reliable servicing of voice calls between parties. And, as one skilled in the art will appreciate, there are a number of timing and latency requirements associated with transmission and reception of voice data in order to maintain quality of service. As such, so-called circuit switched voice links have been fielded that guarantee this quality of service.
And although wireless cellular network technologies have continued to provide improvements related to the ability to process voice calls, there has also been an enormous pull on the industry to provide for the reliable and efficient transfer of packetized data. As a result, the incremental developments in high speed packetized data networks have not always tracked with the development of voice networks. It is a goal within the industry to field a more unified solution that would provide both reliable voice and high speed data access, however, the industry is not at that point presently. Consequently, it is common practice to field a mobile system that provides for voice communications over one type of circuit switched network, say CDMA2000 1xRTT, and high speed data communications over another type of network, say LTE, which provides exclusively for packetized data and does not provide the quality of service that users prefer to support voice communications. In the near future, these hybrid solutions will be prevalent within the art.
In order to field such a hybrid system, designers are forced to develop protocols for those instances where two or more co-fielded networks create conflict, or where two or more co-fielded networks are required to interoperate.
This application deals with one such instance, that is, the switching between a high speed data network that provides exclusively for packetized data communications over to a circuit switched voice network in order to process and incoming or outgoing call or other circuit switched event, and more specifically, how such switching is presently affected utilizing a back end interworking solution that bridges circuit switched notifications through a packetized data “tunnel” in order to communicate these notifications to a mobile station.
In particular, protocols exist for fallback to a circuit switched network during a high speed data session in order to process an incoming or outgoing call. Most present day techniques follow a form of “tunneling,” where notification data associated with the call is encapsulated into a sequence of data units that are exchanged over the packetized data network. And while effective, the present inventors have noted that special purpose hardware and programming is required as part of the overall architecture in order to provide this capability.
Accordingly, what is needed is a technique that would allow a mobile station to be notified of or to provide notification for a circuit switched event while communicating over a packetized data network, where tunneled messages and commensurate back end hardware/software is not required.